Zn(ClO4)2·6H2O as Lewis Acid: New Applications in Organic Synthes

Zn(ClO4)2·6H2O as Lewis Acid: New Applications in Organic Synthesis Giuseppe Bartoli,a Marcella Bosco,a Manuela Locatelli,a Massimo Massaccesi,a Enrico Marcantoni,b Paolo Melchiorre,a Letizia Sambria a) Dipartimento di Chimica Organica “A. Mangini”, Università degli Studi di Bologna, v.le Risorgimento 4, 40136 Bologna, Italy, letizia.sambri@unibo.it b) Dipartimento Scienze Chimiche, via S.Agostino 1, Università di Camerino, 62032 Camerino, (Macerata), Italy In the last few years, we were interested in the use of anhydrous metallic perchlorates as Lewis acid promoters in various organic transformations. LiClO4 and Mg(ClO4)2 showed increased efficiency if hot-dried under vacuum before use. Owing to the potential hazards connected with the heating of such salts, we focused our attention to more efficient perchlorates, active even in the presence of water. In fact, Zn(ClO4)2·6H2O was recently found to behave as a powerful catalyst in the acylation of alcohols and in the synthesis of N-substituted b-enamino esters. As a part of our research program devoted to the development of new Lewis acid systems, we report here that Zn(ClO4)2·6H2O can act as a powerful catalyst for the protection of aryl amines as mono-Boc-derivatives. Moreover, Zn(ClO4)2·6H2O showed to be able to promote the reaction of various functionalized alkyl amines with Boc2O to give the corresponding N-Boc protected derivative. Moreover works are in progress in our laboratory to study the reaction of alcohols with Boc2O in the presence of perchlorate salts.